S898
Clinical - Mixed sites & palliation
ESTRO 2026
cumulative toxicity to surrounding normal tissues. This study aims to provide a systematic review of the literature evaluating the feasibility, safety, and efficacy of hypo-PT in the reRT setting. Material/Methods: PRISMA-compliant systematic review was performed on 2nd October 2025. Full-texts on re-RT with PT in adult patients were considered eligible whenever the delivered dose/fraction was greater than 2 GyRBE/fraction. Bening tumors, non-PT treatments (namely carbon ions, photons, etc.), pre-clinical, in silico, and dosimetric analyses were excluded.All tumor sites were considered. Oncological and toxicity outcomes were retrieved. Results: A total of 16 works were retrieved. The most frequently reported cancers were of head and neck (HN) origin (n = 5); three studies described primary cancers of each lung, gastro-intestinal, and the eye, while two focused on central nervous system tumors. Of these 16 works, 14 were non-overlapping patients’ series and were considered within the scope of this work. The most relevant characteristics of the selected papers are reported in Table 1. The total number of patients treated with hypo-PT was 511. A summary of the total number of patients considered for each sub- site and the prescribed doses is shown in Figure 1. Despite the highest number of papers referred to HN cancers, the majority of patients were treated for recurrent tumors of either the gastrointestinal (GI) region (n=143) or the lung (n=123). Median sample size was 30 (interquartile range: 23- 45). Moderate hypofractionation (< 5 Gy/fraction) was the most frequent schedule. The widest range of fractionation was found among patients treated for lung tumors (from 2.1 to 18 GyRBE/fraction). All included studies had a radical intent and reported both on clinical outcomes and toxicity profiles.
Conclusion: Radiotherapy dose escalation did not improve OS in oesophageal or lung cancers. Short-term PFS gains with higher-dose radiotherapy in oesophageal cancer did not persist at longer follow-up and were not supported by randomized data or EQD2 dose– response modelling. For lung cancer, no association between dose and survival was identified. These findings indicate no consistent survival advantage from dose escalation in these tumour sites and support evaluation of alternative therapeutic strategies beyond increasing radiotherapy dose. References: 1. Yao Y, Lu J, Qin Z, Li N, Ma J, Yao N, Qu W, Cui L, Yuan S, Jiang A, Liu X. High-dose versus standard-dose radiotherapy in concurrent chemoradiotherapy for inoperable esophageal cancer: A systematic review and meta-analysis. Radiother Oncol. 2023 Jul;184:109700. 2. Bradley JD, Paulus R, Komaki R, et al: Standard-dose versus high-dose conformal radiotherapy with concurrent and consolidation carboplatin plus paclitaxel with or without cetuximab for patients with stage IIIA or IIIB non-small-cell lung cancer (RTOG 0617): a randomised, two-by-two factorial phase 3 study. The Lancet Oncology 16:187– 199, 2015. Keywords: Myelopathy, spinal cord, radiotherapy dose Digital Poster 3534 Reirradiation with Proton Therapy Using Hypofractionated Schedules:a Systematic Review of the Literature Daniela Alterio, Vanessa Pierini, Stefania Volpe, Maria Giulia Vincini, Annamaria Ferrari, Barbara Alicja Jereczek-Fossa Radiation Oncology, IEO, IRCCS, Milan, Italy Purpose/Objective: In the re-irradiation (reRT) setting, hypofractionation offers the potential for enhanced tumor control and treatment efficiency but raises concerns regarding
Conclusion: The present analysis showed that only a limited number of patients have received hypofractionated re- RT with PT. The majority of the published series refers to retrospective and monoinstitutional experiences. Evidence supporting the use of hypofractionated PT
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